Axial flow fan

ABSTRACT

The invention relates to an axial flow fan (1) comprising a stationary hub (2); comprising an annular stationary frame (3), which surrounds the hub (2) on the outer peripheral side and which is connected to the stationary hub (2) via at least one strut (4, 5, 6); and comprising a fan wheel (8), which is in drive connection with a fan wheel drive (9), which has a rotating fan wheel hub (10), and which has a plurality of fan wheel blades (11), which each comprise a back edge (12), characterized in that the contour of the strut (4, 5, 6) is designed as sine wave shaped, and wherein the back edge (12) is preferably designed as toothed at least in a partial area (13).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German Patent Application No. 102017210632.8 filed Jun. 23, 2017, the disclosure of which is herein incorporated by reference in its entirety.

DESCRIPTION

The invention relates to an axial flow fan according to the preamble of claim 1.

An axial flow fan of this type is known from DE 10 2010 039 219 A1. In addition to achieving a maximum aerodynamic efficiency, this axial flow fan should also simultaneously prevent noise created by air flowing past the fan.

To achieve these goals, DE 10 2010 039 219 A1 teaches about a fan, which is provided in particular as an engine cooling fan in a motor vehicle, in which a stationary frame surrounds a rotating fan wheel and the fan wheel comprises fan blades which are enclosed by a fan shroud, wherein the fan shroud forms a gap with the frame. According to the invention of this document, a secondary fan is additionally provided which prevents a return flow of the air conveyed by the fan wheel. For example, the secondary fan may be a component of the fan wheel and, in a preferred embodiment, is constructed of secondary fan blades arranged on the fan shroud.

The disadvantage of this arrangement is predominantly a relatively high construction expense for the arrangement and design of the secondary fan, and tests carried out in the scope of the invention have additionally demonstrated that additional noise minimization is desirable.

It is therefore the object of the present invention to create an axial flow fan as indicated in the preamble of claim 1, which enables an aerodynamic optimization with additional noise minimization.

The solution to this problem is carried out by the features of claim 1.

Correspondingly, an axial flow fan according to the invention is provided, which has a stationary hub, which is surrounded on the peripheral side by a stationary frame, which is connected to the hub via at least one strut. The fan wheel has a rotatable fan wheel hub, which is in drive connection through an internal combustion engine with a fan wheel drive, such as an electric motor, a viscous coupling, or a direct drive. Furthermore, the fan wheel has a plurality of fan wheel blades, which are fixed on the fan wheel hub and conventionally extend radially outwardly from the fan wheel hub to a peripheral side fan collar, wherein the fan wheel blades are fixed both on the hub and also to the fan collar.

To achieve the goals according to the invention, the contour of the strut may be designed in a sine wave shape. Due to the sine wave shaped contour of the strut, an aerodynamic optimization of this component is possible, which leads, in particular, to a reduced air resistance, and additionally also facilitates producibility and simultaneously ensures the structural stability of the strut. The aerodynamic optimization facilitates noise minimization.

The subclaims contain as subject matter advantageous refinements of the invention.

It is particularly preferred if a back edge of the fan wheel blades is designed as toothed at least in a partial area.

Due to the combination of the at least partially toothed back edge with the sine wave shaped contour of the struts, it is possible to reduce the amplitude of pressure shaped contour of the struts, it is possible to reduce the amplitude of pressure pulsation during passage through the fan wheel blades, which also substantially facilitates noise minimization.

It is additionally possible, in a particularly preferred embodiment, to provide a plurality of struts, of which each may have a sine wave shaped contour. It is hereby additionally possible to divide the plurality of struts into strut groups of, e.g., three struts respectively, which may be arranged spaced apart from one another between the stationary hub and the frame.

When forming the strut groups, relatively thin struts may be used. Alternatively, wider struts may be used, in particular in a uniform arrangement.

In one particularly preferred embodiment, the sine wave shaped contour arises due to a sine wave shaped embodiment of the front side of the strut or of all struts. If relatively thin struts are used, then the “front side” may also be designated as the “front edge”.

The front side or front edge faces the fan wheel blades with respect to the axial direction of the axial flow fan. The elevations of the sine wave shaped contours thus extend in the axial direction and are closer to the fan wheel then the valleys located between the elevations of the sine wave shaped contour.

To further improve the noise behavior, it is possible to design the struts asymmetrically and, in another preferred embodiment, to incline the flow surfaces of the struts from inward to outward, when viewed in the flow direction.

As previously explained, the design according to the invention of the struts arises from an optimization of their geometry, in particular to achieve a low air resistance.

In principle, it is possible to arrange the fan wheel blades of the fan wheel as uniformly spaced, thus at the same angular distance to one another on the fan wheel hub.

However, a uniform spacing of the fan wheel blades produces additional advantages with respect to the optimization of noise minimization.

The toothed partial area of the back edge of the fan wheel blades is arranged adjacent to the frame in one particularly preferred embodiment. In principle, it is also possible, however, to design the entire back edge as toothed.

A non-parallel arrangement of the front edge of the strut or struts to the back edge of the fan wheel blades produces additional aerodynamic and noise-minimizing effects.

The sine wave shaped contour of the individual struts preferably has an amplitude of at least 1 mm, particularly preferably at least 1.5 mm. The amplitude is measured parallel to the axial direction of the axial flow fan and thus describes the height of the individual elevations formed by the sine wave shaped contour.

The sine wave shaped contour of the individual struts preferably has at least two, particularly preferably at least three elevations and corresponding valleys between the elevations.

Additional details, features, and advantages of the present invention arise from the subsequent description of an embodiment by way of the drawings. As shown in:

FIG. 1 a perspective view of an axial flow fan according to the invention,

FIG. 2 a perspective partial depiction of an area of the fan wheel, the frame, and the hub of the axial flow fan according to the invention according to FIG. 1, and

FIG. 3 a perspective partial depiction of an area of the fan wheel, the frame, and the hub of the axial flow fan of a variant of the axial flow fan according to the invention.

FIG. 1 shows an axial flow fan 1 according to the invention which has a stationary hub 2 and a stationary frame 3 surrounding hub 2 on the outer peripheral side. Frame 3 is, in the example case, designed as annular and has a trough shaped outer contour on which fastening lugs may be applied of which three lugs are visible in FIG. 1 and are designated with the reference numerals 21, 22, and 23.

Hub 2 and frame 3 may be connected to one another via a strut, wherein the particularly preferred embodiment depicted in FIG. 1 comprises a plurality of struts, of which three are designated with reference numerals 4, 5, and 6. As is clear in FIG. 1, a total of 18 of these types of struts 4, 5, and 6 are provided in this embodiment which are respectively collected into triplet groups 14, 15, 16, 17, 18, or 19. Struts 4, 5, and 6 are arranged closely adjacent in said triplet groups 14 through 19, and the triplet groups are each arranged at the same angular distance between hub 2 and frame 3, as this is shown in detail in the depiction of FIG. 1.

Axial flow fan 1 according to FIG. 1 additionally has a fan wheel 8, which may be driven by means of a suitable fan drive 9, which is symbolized in FIG. 1 by a dashed circle. Fan drive 9 may be arranged, e.g., in stationary hub 2.

Fan wheel 8 additionally has a rotatable fan wheel hub 10, on which a plurality of fan wheel blades is arranged, of which one fan wheel blade is designated in FIG. 1 with reference numeral 11 as representative for all fan wheel blades. In the embodiment depicted in FIG. 1, the fan wheel blades extend from fan wheel hub 10 up to an outer encompassing fan collar 20, as this is shown in detail in the depiction of FIG. 1.

As is clear from an overview of FIGS. 1 and 2, the contours of struts 4, 5, and 6 is designed as sine wave shaped, wherein the sine wave shaped design arises from the sine wave shaped course of a front edge 7 of struts 4, 5, and 6 in the particularly preferred embodiment shown in FIG. 2.

Furthermore, FIG. 2 illustrates in particular that a back edge 12 of fan wheel blades 11 is designed as toothed at least in a partial area 13. In the embodiment depicted in FIG. 2, toothed partial area 13 connects to the frame and extends across a partial section of back edge 12 in the direction of hub 2. It is basically also possible, to design entire back edge 12 as toothed.

As is additionally clear from FIG. 2, struts 4, 5, and 6 have inflow surfaces, of which inflow surface 24 as represented on strut 4 is designated as representative of all inflow surfaces. Said inflow surface 24 is inclined from inside to outside when viewed in the inflow direction on the strut.

In the embodiment depicted in FIGS. 1 and 2, the fan wheel blades are provided spaced uniformly apart from one another.

FIG. 3 shows that wider struts 4 may also be used instead of the relatively thin struts from FIGS. 1 and 2. According to FIG. 3, front side 7 of strut 4 has the sine wave shaped contour. Front side 7 transitions into inflow surface 24 with a flow optimized radius R. Radius R is preferably at least 3 mm, particularly preferably at least 5 mm.

It is, however, also possible to provide fan wheel blades 11 in unequal distances to one another which, at least in many embodiments, may produce another improvement in the noise behavior of axial flow fan 1 according to the invention.

In addition to the preceding written disclosure of the invention, reference is hereby explicitly made to the graphic representation of the invention in FIGS. 1 and 2 as a supplemental disclosure.

REFERENCE SIGN LIST

-   1 Axial flow fan -   2 Hub -   3 Frame -   4, 5, 6 Struts -   7 Front side, also; front edge -   8 Fan wheel -   9 Fan wheel drive -   10 Fan wheel hub -   11 Fan wheel blades -   12 Back edge -   13 Partial area -   14-19 Strut groups/triplet groups -   20 Fan collar -   21-23 Fastening lugs -   24 Inflow surface 

1. An axial flow fan (1) comprising a stationary hub (2); comprising an annular stationary frame (3), which surrounds the hub (2) on the outer peripheral side and which is connected to the stationary hub (2) via at least one strut (4, 5, 6); and comprising a fan wheel (8), which is in drive connection with a fan wheel drive (9), which has a rotating fan wheel hub (10), and which has a plurality of fan wheel blades (11), which each comprise a back edge (12), wherein the back edge (12) faces the at least one strut (4, 5, 6), characterized in that the contour of the strut (4, 5, 6) is designed as sine wave shaped, and wherein the back edge (12) is preferably designed as toothed at least in a partial area (13).
 2. The axial flow fan according to claim 1, characterized in that a plurality of struts (4, 5, 6) is provided, of which each has a sine wave shaped contour.
 3. The axial flow fan according to claim 2, characterized in that the plurality of struts (4, 5, 6) is distributed in strut groups (14-19) arranged spaced apart from one another.
 4. The axial flow fan according to claim 1, characterized in that the strut (4, 5, 6) has a front side (7) which is designed as sine wave shaped.
 5. The axial flow fan according to claim 1, characterized in that the strut (4, 5, 6) is designed as asymmetrical.
 6. The axial flow fan according to claim 1, characterized in that the strut (4, 5, 6) has an inflow surface (24) which inclines from inside to outside when viewed in the flow direction.
 7. The axial flow fan according to claim 1, characterized in that the geometry of the strut (4, 5, 6) is aerodynamically optimized to achieve a low air resistance.
 8. The axial flow fan according to claim 1, characterized in that the fan wheel blades (11) are arranged spaced equally apart from one another.
 9. The axial flow fan according to claim 1, characterized in that the fan wheel blades (11) are arranged spaced unequally apart from one another.
 10. The axial flow fan according to claim 1, characterized in that the toothed partial area (13) is arranged adjacent to the frame (3).
 11. The axial flow fan according to claim 4, characterized in that the front side (7) of the strut (4, 5, 6) is not arranged parallel to the back edge (12) of the fan wheel blades (11). 